2014/11/30 by André H. Hoang, Daniel W. Kolodrubetz, Vicent Mateu +1 · 1 citation
Physics and Astronomy · #hep-ph
paper · pdf · doi:10.1103/physrevd.91.094017
published as Phys. Rev. D 91, 094017 (2015) · 34 pages, 20 figures
arxiv created 2015/05/26 · arxiv updated 2015/05/27
We compute the e+ e- C-parameter distribution using the Soft-Collinear Effective Theory with a resummation to N3LL^′ accuracy of the most singular partonic terms. This includes the known fixed-order QCD results up to \cal O (αs3), a numerical determination of the two loop non-logarithmic term of the soft function, and all logarithmic terms in the jet and soft functions up to three loops. Our result holds for C in the peak, tail, and far tail regions. Additionally, we treat hadronization effects using a field theoretic nonperturbative soft function, with moments Ωn. In order to eliminate an \cal O (Λ\rm QCD) renormalon ambiguity in the soft function, we switch from the \rm MS to a short distance "Rgap" scheme to define the leading power correction parameter Ω1. We show how to simultaneously account for running effects in Ω1 due to renormalon subtractions and hadron mass effects, enabling power correction universality between C-parameter and thrust to be tested in our setup. We discuss in detail the impact of resummation and renormalon subtractions on the convergence. In the relevant fit region for αs(mZ) and Ω1, the perturbative uncertainty in our cross section is ≃ 3% at Q=mZ.